Modeling the intraurban variability of ambient traffic pollution in Toronto, Canada

The objective of this paper is to model determinants of intraurban variation in ambient concentrations of nitrogen dioxide (NO2) in Toronto, Canada, with a land use regression (LUR) model. Although researchers have conducted similar studies in Europe, this work represents the first attempt in a North American setting to characterize variation in traffic pollution through the LUR method. NO2 samples were collected over 2 wk using duplicate two-sided Ogawa passive diffusion samplers at 95 locations across Toronto. Independent variables employed in subsequent regression models as predictors of NO2 were derived by the Arc 8 geographic information system (GIS). Some 85 indicators of land use, traffic, population density, and physical geography were tested. The final regression model yielded a coefficient of determination (R2) of .69. For the traffic variables, density of 24-h traffic counts and road measures display positive associations. For the land use variables, industrial land use and counts of dwellings within 2000 m of the monitoring location were positively associated with NO2. Locations up to 1500 m downwind of major expressways had elevated NO2 levels. The results suggest that a good predictive surface can be derived for North American cities with the LUR method. The predictive maps from the LUR appear to capture small-area variation in NO2 concentrations. These small-area variations in traffic pollution are probably important to the exposure experience of the population and may detect health effects that would have gone unnoticed with other exposure estimates.

An exploratory spatial analysis of pneumonia and influenza hospitalizations in Ontario by age and gender

Pneumonia and influenza represent a significant public health burden in Canada and abroad. Knowledge of how this burden varies geographically provides clues to understanding the determinants of these illnesses, and insight into the effective management of health-care resources. We conducted a retrospective, population-based, ecological-level study to assess age- and gender-specific spatial patterns of pneumonia and influenza hospitalizations in the province of Ontario, Canada from 1992 to 2001. Results revealed marked variability in hospitalization rates by age, as well as clear and statistically significant patterns of high rates in northern rural counties and low rates in southern urban counties. A moderate yet significant level of positive spatial autocorrelation (Moran's I=0.21, P<0.05) was found in the global data, with significant, age-specific clusters of high values or 'hot spots' identified in several northern counties. Findings illustrate the need for geographically focused prevention strategies, and resource and service allocation policies informed by regional and population-specific demands.

Do socioeconomic characteristics modify the short term association between air pollution and mortality? Evidence from a zonal time series in Hamilton, Canada

STUDY OBJECTIVE

To assess the short term association between air pollution and mortality in different zones of an industrial city. An intra-urban study design is used to test the hypothesis that socioeconomic characteristics modify the acute health effects of ambient air pollution exposure.

DESIGN

The City of Hamilton, Canada, was divided into five zones based on proximity to fixed site air pollution monitors. Within each zone, daily counts of non-trauma mortality and air pollution estimates were combined. Generalised linear models (GLMs) were used to test mortality associations with sulphur dioxide (SO(2)) and with particulate air pollution measured by the coefficient of haze (CoH).

MAIN RESULTS

Increased mortality was associated with air pollution exposure in a citywide model and in intra-urban zones with lower socioeconomic characteristics. Low educational attainment and high manufacturing employment in the zones significantly and positively modified the acute mortality effects of air pollution exposure.

DISCUSSION

Three possible explanations are proposed for the observed effect modification by education and manufacturing: (1) those in manufacturing receive higher workplace exposures that combine with ambient exposures to produce larger health effects; (2) persons with lower education are less mobile and experience less exposure measurement error, which reduces bias toward the null; or (3) manufacturing and education proxy for many social variables representing material deprivation, and poor material conditions increase susceptibility to health risks from air pollution.

An analysis of migratory systems: 2. Operational framework

"This is the second in a series of three interrelated papers which aim to combine evolutionary migration models with stochastic utility theory. The first paper dealt with migratory dynamics. Here the details are given of a choice model, established by McFadden, which can be used in conjunction with migratory dynamics thus providing an explicit link between the macroproperties of the population system and human behaviour. First, the structure of transition probabilities is derived under a two-level decision to migrate. An argument is then given about the empirical form of these probabilities, and the discussion closes with a method which can be used for their maximum likelihood estimation."

An analysis of migratory systems: 1. Theory

This is the first of a planned series of three papers in which the authors attempt to combine evolutionary migration models with stochastic utility theory. This first paper deals with the evolution of migratory systems. Such systems are first defined, and the foundations upon which their evolution is based are described. The paper concludes with a discussion of disequilibrium, which is central to the series. "Disequilibrium is related to the concept of a steady state, the existence of which is established for nonlinear migratory systems of the type discussed here."

Metropolitan elderly out-migration in Canada, 1971-1976. Characterization and explanation

This article analyzes the 1971-1976 out-migration pattern of the Canadian male elderly from the 23 Census Metropolitan Areas (CMAs). Migration is conceptualized within a three-level choice framework, and statistical inference is based on a logit model. The findings include that (1) retirement-oriented migration in Canada takes place long before the official retirement age; (2) compared with the young migrants, the elderly migrants are less likely to be metropolitanward and tend to have a more concentrated destination choice pattern; (3) with respect to metropolitanward elderly migrants from the CMAs, the probability of choosing a particular destination is negatively related to the logarithm of distance, cultural dissimilarity, coldness, and gross rent, and positively related to population size, brightness, and housing growth; and (4) compared with the young migrants, the elderly migrants are more sensitive to the environmental variables.